Pyranometer measurements of the solar surface radiation (SSR)
are available at many locations worldwide, often as long time series
covering several decades into the past. These data constitute a potential
source of information on the atmospheric aerosol load. Here,
we present a method for estimating the aerosol optical depth (AOD)
using pyranometer measurements of the SSR together with
total water vapor column information. The method, which is
based on radiative transfer simulations, was developed
and tested using recent data from Thessaloniki, Greece.
The effective AOD calculated using this method was found to
agree well with co-located AERONET measurements, exhibiting
a correlation coefficient of 0.9 with 2/3 of the data
found within &plusmn;20% or &plusmn;0.05 of the AERONET AOD. This is
similar to the performance of current satellite aerosol methods. Differences in the
AOD as compared to AERONET can be explained by variations in the
aerosol properties of the atmosphere that are not accounted for in
the idealized settings used in the radiative transfer simulations, such as
variations in the single scattering albedo and Ångström exponent.
Furthermore, the method is sensitive to calibration offsets between the
radiative transfer simulations and the pyranometer SSR. The method
provides an opportunity of extending our knowledge of the
atmospheric aerosol load to locations and times not covered by
dedicated aerosol measurements.